1. Field of the Invention
The present invention relates to a device for objectively evaluating the quality of a digital transmitted picture and, more particularly, to a device for objectively evaluating the quality of a digital transmitted picture, suitable for use in a system in which a video picture is compressed, encoded and transmitted on a plurality of links, so as to improve the reliability of transmission.
2. Description of the Related Art
There have been conventionally studied and developed automatic quality measurements (objective picture quality evaluations) of a digital compressed picture, thus offering various proposals. Such objective picture quality evaluations include a first method for evaluating a picture quality based on the comparison of a received picture with an original picture after the model of human subjective evaluations and a second method for evaluating a picture quality based on only a received picture.
In the first method, that is, the method using an original picture, a picture quality can be evaluated with high accuracy. This method is disclosed in detail in, for example, the following literature: T. Hamada, et al., xe2x80x9cPicture Quality Assessment System by Three-layered Bottom-up Noise Weighting Considering Human Visual Perception,xe2x80x9d SMPTE Journal, Vol. 108, No. 1, pp. 20-26, January, 1999.
If the quality of a received picture is to be evaluated by the second method, namely, the quality of a received picture is to be evaluated during actual transmission of a digital compressed picture, its original picture cannot be used for the evaluation, so that the method disclosed in the aforementioned literature cannot be adopted.
As described above, if the quality of the received picture is to be evaluated during the actual transmission of the picture, the picture quality must be evaluated based on only the received picture since its original picture cannot be used. Nevertheless, there has not been conventionally made any marked proposal for the above-described evaluation.
An object of the present invention is to provide a device for objectively evaluating the quality of a digital transmitted picture, in which the quality of a received picture can be objectively evaluated with high accuracy by using only the received picture in the compression encoding transmission of a picture on a plurality of links.
In order to achieve the above-described object, the present invention provides a device for objectively evaluating the quality of a digital transmitted picture to be transmitted in a transmission system consisting of a plurality of links, in which the device comprises means for measuring a variance value of a received picture on one of the plurality of links, means for measuring a variance value of a signal indicative of a difference between the received picture on one of the plurality of links and another received picture on the other link, and means for holding therein a corresponding table indicative of relationship between the two variance values and SN ratios of the received pictures to an original picture, the quality of the received picture being evaluated in reference to the corresponding table based on the two variance values.
Furthermore, the present invention provides a device for objectively evaluating the quality of a digital transmitted picture to be transmitted in a transmission system consisting of a plurality of links, therein an original picture and a received picture are subjected to a filtration.
According to the present invention, it is possible to estimate the SN ratio of the received picture to the original picture or the SN ratio weighted with the visual characteristics by using only the received pictures on the two links in the compression encoding transmission of the picture on the plurality of links.